From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7DDEACFD376 for ; Fri, 28 Nov 2025 09:33:03 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D2F716B0005; Fri, 28 Nov 2025 04:33:02 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id D074A6B0026; Fri, 28 Nov 2025 04:33:02 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C1CF66B0031; Fri, 28 Nov 2025 04:33:02 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id ADBC86B0005 for ; Fri, 28 Nov 2025 04:33:02 -0500 (EST) Received: from smtpin27.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 6E19F505C7 for ; Fri, 28 Nov 2025 09:33:02 +0000 (UTC) X-FDA: 84159501804.27.DA32626 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf30.hostedemail.com (Postfix) with ESMTP id BAE1C80009 for ; Fri, 28 Nov 2025 09:33:00 +0000 (UTC) Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="dNM/q7O+"; spf=pass (imf30.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1764322380; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=njNMsPFFVo0oglT3ZjeP3MprL0cXf1wmeIChcnzbz4Y=; b=8HvcH8zZm9ViOO3Uf8/0ZBPHtJZOXKRrnYI3oZhWN7+gMQnZ5fg7hp3b98Q8mx/DySbc6I uQJ5jO/xOx6Hln3jevJa+0BDkutaDcw3mVPADowIlDuB0XTkQD2dq1CkoyZ/6oOo0vueLV GwdV/WdkpclupmRB/qi1Pvrj826UpNQ= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1764322380; a=rsa-sha256; cv=none; b=G3sbTA4iHpZm0G1Z3euFKMNksMV0BwUSu1e/Fb4ohErvO5fYj2XA12GVSoN/D1ufxBdyKa yLdHj3ZB7L4nLH8h4a8Y4ndRdHo+QILXJKjhRKHDkOK2ppjpllmwEG/6649YLnNFgEZSW2 N6s0oRa6+CYVV9owhrJhA0hsRJDlFyY= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="dNM/q7O+"; spf=pass (imf30.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 0D6B560225; Fri, 28 Nov 2025 09:33:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A3220C2BCB3; Fri, 28 Nov 2025 09:32:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764322379; bh=ax3ZOoXlAAXf0E1NKzt1mIJarEydCCkiax1Sg5VyIqw=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=dNM/q7O+Q/6NnEzCCUed7ld+KJdoKuokwlWfnkkD/a71Rft62arVXl4eCr1vBlU1F WmfuBjD3c68G/GyQkXJqEq1L2sddXqE2tJRpZFDWwC2vs/A/8kY6AhAzsw5/FLrkyV R4VcXTepa2qlFffv/FxJo5h+nbpbv2PhizYFygfVBEFX6lJVMIpmCSXvKdP6XxbV2r 23Z914SEMznasS6bYwwWVEA96zf4yMsYlWsvkUqtLhSJ5TxgPFqfrz8+MNEUcgjzBY qSQxClNL3389d0tOtHBMrqO0dbZbmuyw0r9nBcV2T6aRXCH6PreZxJtltd1llwxusk nxvIjMXVVvEPQ== Message-ID: Date: Fri, 28 Nov 2025 10:32:53 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 2/4] mm: Add support for unaccepted memory hotplug To: "Pratik R. Sampat" , linux-mm@kvack.org, linux-coco@lists.linux.dev, linux-efi@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, kas@kernel.org, ardb@kernel.org, akpm@linux-foundation.org, osalvador@suse.de, thomas.lendacky@amd.com, michael.roth@amd.com References: <20251125175753.1428857-1-prsampat@amd.com> <20251125175753.1428857-3-prsampat@amd.com> From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: <20251125175753.1428857-3-prsampat@amd.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: BAE1C80009 X-Stat-Signature: m1fsi4ouckgxr9xdzuyj5mpwjc1sn3so X-HE-Tag: 1764322380-612940 X-HE-Meta: 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 /LfCm4e5 pjlOz56bbdoUblTiywafGWI2mv+Zt3Lh71iMz6JmUarZ+5/f2jLpoIvF+8hSfishPM/Am9DCyYYpY56AmMAOCnZ/FeN1dos9w+wc1BnII5Mu9dJDP9Kyd7UQS44XO37ruAdbc/X3R8Waa8V+JxEbXe2yR09HFk9CfkXTiDFdPmWXTGzOWEsZMHu6704z3feO/XSJ6knpY1IS/TvF6Nmginc4tntOqzs5T4vk4pM7ENgdObwiyZC/ZlDEOsf/k4u4ljE0vZDB1YzuXVEbDiRoH7mEn4ZnfLSBrpLi8ckTAWKfFgNZBsLi228CNH049nGhJWDYi X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 11/25/25 18:57, Pratik R. Sampat wrote: > The unaccepted memory structure currently only supports accepting memory > present at boot time. The unaccepted table uses a fixed-size bitmap > reserved in memblock based on the initial memory layout, preventing > dynamic addition of memory ranges after boot. This causes guest > termination when memory is hot-added in a secure virtual machine due to > accessing pages that have not transitioned to private before use. > > Extend the unaccepted memory framework to handle hotplugged memory by > dynamically managing the unaccepted bitmap. Allocate a new bitmap when > hotplugged ranges exceed the reserved bitmap capacity and switch to > kernel-managed allocation. > > Hotplugged memory also follows the same acceptance policy using the > accept_memory=[eager|lazy] kernel parameter to accept memory either > up-front when added or before first use. > > Signed-off-by: Pratik R. Sampat > --- > arch/x86/boot/compressed/efi.h | 1 + > .../firmware/efi/libstub/unaccepted_memory.c | 1 + > drivers/firmware/efi/unaccepted_memory.c | 83 +++++++++++++++++++ > include/linux/efi.h | 1 + > include/linux/mm.h | 11 +++ > mm/memory_hotplug.c | 7 ++ > mm/page_alloc.c | 2 + > 7 files changed, 106 insertions(+) > > diff --git a/arch/x86/boot/compressed/efi.h b/arch/x86/boot/compressed/efi.h > index 4f7027f33def..a220a1966cae 100644 > --- a/arch/x86/boot/compressed/efi.h > +++ b/arch/x86/boot/compressed/efi.h > @@ -102,6 +102,7 @@ struct efi_unaccepted_memory { > u32 unit_size; > u64 phys_base; > u64 size; > + bool mem_reserved; > unsigned long *bitmap; > }; > > diff --git a/drivers/firmware/efi/libstub/unaccepted_memory.c b/drivers/firmware/efi/libstub/unaccepted_memory.c > index c1370fc14555..b16bd61c12bf 100644 > --- a/drivers/firmware/efi/libstub/unaccepted_memory.c > +++ b/drivers/firmware/efi/libstub/unaccepted_memory.c > @@ -83,6 +83,7 @@ efi_status_t allocate_unaccepted_bitmap(__u32 nr_desc, > unaccepted_table->unit_size = EFI_UNACCEPTED_UNIT_SIZE; > unaccepted_table->phys_base = unaccepted_start; > unaccepted_table->size = bitmap_size; > + unaccepted_table->mem_reserved = true; > memset(unaccepted_table->bitmap, 0, bitmap_size); > > status = efi_bs_call(install_configuration_table, > diff --git a/drivers/firmware/efi/unaccepted_memory.c b/drivers/firmware/efi/unaccepted_memory.c > index 4479aad258f8..8537812346e2 100644 > --- a/drivers/firmware/efi/unaccepted_memory.c > +++ b/drivers/firmware/efi/unaccepted_memory.c > @@ -218,6 +218,89 @@ bool range_contains_unaccepted_memory(phys_addr_t start, unsigned long size) > return ret; > } > > +static int extend_unaccepted_bitmap(phys_addr_t mem_range_start, > + unsigned long mem_range_size) > +{ > + struct efi_unaccepted_memory *unacc_tbl; > + unsigned long *old_bitmap, *new_bitmap; > + phys_addr_t start, end, mem_range_end; > + u64 phys_base, size, unit_size; > + unsigned long flags; > + > + unacc_tbl = efi_get_unaccepted_table(); > + if (!unacc_tbl || !unacc_tbl->unit_size) > + return -EIO; > + > + unit_size = unacc_tbl->unit_size; > + phys_base = unacc_tbl->phys_base; > + > + mem_range_end = round_up(mem_range_start + mem_range_size, unit_size); > + size = DIV_ROUND_UP(mem_range_end - phys_base, unit_size * BITS_PER_BYTE); > + > + /* Translate to offsets from the beginning of the bitmap */ > + start = mem_range_start - phys_base; > + end = mem_range_end - phys_base; > + > + old_bitmap = efi_get_unaccepted_bitmap(); > + if (!old_bitmap) > + return -EIO; > + > + /* If the bitmap is already large enough, just set the bits */ > + if (unacc_tbl->size >= size) { > + spin_lock_irqsave(&unaccepted_memory_lock, flags); > + bitmap_set(old_bitmap, start / unit_size, (end - start) / unit_size); > + spin_unlock_irqrestore(&unaccepted_memory_lock, flags); > + > + return 0; > + } > + > + /* Reserved memblocks cannot be extended so allocate a new bitmap */ > + if (unacc_tbl->mem_reserved) { > + new_bitmap = kzalloc(size, GFP_KERNEL); > + if (!new_bitmap) > + return -ENOMEM; > + > + spin_lock_irqsave(&unaccepted_memory_lock, flags); > + memcpy(new_bitmap, old_bitmap, unacc_tbl->size); > + unacc_tbl->mem_reserved = false; > + free_reserved_area(old_bitmap, old_bitmap + unacc_tbl->size, -1, NULL); > + spin_unlock_irqrestore(&unaccepted_memory_lock, flags); > + } else { > + new_bitmap = krealloc(old_bitmap, size, GFP_KERNEL); > + if (!new_bitmap) > + return -ENOMEM; > + > + /* Zero the bitmap from the range it was extended from */ > + memset(new_bitmap + unacc_tbl->size, 0, size - unacc_tbl->size); > + } > + > + bitmap_set(new_bitmap, start / unit_size, (end - start) / unit_size); > + > + spin_lock_irqsave(&unaccepted_memory_lock, flags); > + unacc_tbl->size = size; > + unacc_tbl->bitmap = (unsigned long *)__pa(new_bitmap); > + spin_unlock_irqrestore(&unaccepted_memory_lock, flags); > + > + return 0; > +} > + > +int accept_hotplug_memory(phys_addr_t mem_range_start, unsigned long mem_range_size) > +{ > + int ret; > + > + if (!IS_ENABLED(CONFIG_UNACCEPTED_MEMORY)) > + return 0; > + > + ret = extend_unaccepted_bitmap(mem_range_start, mem_range_size); > + if (ret) > + return ret; > + > + if (!mm_lazy_accept_enabled()) > + accept_memory(mem_range_start, mem_range_size); > + > + return 0; > +} > + > #ifdef CONFIG_PROC_VMCORE > static bool unaccepted_memory_vmcore_pfn_is_ram(struct vmcore_cb *cb, > unsigned long pfn) > diff --git a/include/linux/efi.h b/include/linux/efi.h > index a74b393c54d8..1021eb78388f 100644 > --- a/include/linux/efi.h > +++ b/include/linux/efi.h > @@ -545,6 +545,7 @@ struct efi_unaccepted_memory { > u32 unit_size; > u64 phys_base; > u64 size; > + bool mem_reserved; > unsigned long *bitmap; > }; > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 1ae97a0b8ec7..bb43876e6c47 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -4077,6 +4077,9 @@ int set_anon_vma_name(unsigned long addr, unsigned long size, > > bool range_contains_unaccepted_memory(phys_addr_t start, unsigned long size); > void accept_memory(phys_addr_t start, unsigned long size); > +int accept_hotplug_memory(phys_addr_t mem_range_start, > + unsigned long mem_range_size); > +bool mm_lazy_accept_enabled(void); > > #else > > @@ -4090,6 +4093,14 @@ static inline void accept_memory(phys_addr_t start, unsigned long size) > { > } > > +static inline int accept_hotplug_memory(phys_addr_t mem_range_start, > + unsigned long mem_range_size) > +{ > + return 0; > +} > + > +static inline bool mm_lazy_accept_enabled(void) { return false; } > + > #endif > > static inline bool pfn_is_unaccepted_memory(unsigned long pfn) > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 74318c787715..bf8086682b66 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1581,6 +1581,13 @@ int add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) > if (!strcmp(res->name, "System RAM")) > firmware_map_add_hotplug(start, start + size, "System RAM"); > > + ret = accept_hotplug_memory(start, size); What makes this special that we have to have "hotplug_memory" as part of the name? Staring at the helper itself, there isn't anything really hotplug specific happening in there except extending the bitmap, maybe? -- Cheers David